The present invention relates to the improvement of a vehicle multi-cylinder engine that has a plurality of banks each comprising a cylinder row portion and a cylinder head. The plurality of banks are setted at an angle relative to each other and disposed so as to be offset from each other in an axial direction of a crankshaft. The vehicle multi-cylinder engine has a valve operating characteristics changing mechanisms which changes operating characteristics of engine valves in response to oil pressure control implemented by oil pressure control valves. The oil pressure control valves are incorporated in valve trains on the cylinder head of at least one of the plurality of banks.
Conventionally, such a vehicle multi-cylinder engine is described in Japanese patent Publication No. 2741492 and the like.
In a conventional vehicle multi-cylinder engine such as above, a pair of banks disposed in a V-shape are provided integrally on an engine block. A pump body constituting part of a pump case of an oil pump is attached to an end wall of the engine block at one end thereof along the axial direction of a crankshaft. An oil pressure control valve is, in turn, attached to the pump body. These construction results in the placement of the oil pressure control valve at a position which protrudes from the engine in the axial direction of the crankshaft and the enlargement of the overall dimensions of the multi-cylinder engine. However, since both the banks are disposed so as to be offset from each other in the axial direction of the crankshaft, a vacant space should be produced between end portions of both the banks at either end of the banks in the axial direction of the crankshaft. Making effective use of such a vacant space for disposing the oil pressure control valve therein can contribute to making the vehicle multi-cylinder engine compact.
The present invention was made in view of the situation. An object thereof is to provide a vehicle multi-cylinder engine, that an oil pressure control valve is disposed at a position and the position makes it possible to miniaturize the overall vehicle multi-cylinder engine.
With a view to attaining the object, according to the first aspect of the invention, there is provided A vehicle multi-cylinder engine comprising: a plurality of banks, each including a cylinder row portion having a plurality of cylinder bores arranged in a row and provided in an engine block, and a cylinder head connected to the cylinder row portion, wherein the plurality of banks are setted at an angle relative to each other on a projection drawing onto a plane normal to an axial direction of a crankshaft and are disposed to be offset from each other in an axial direction of the crankshaft; valve trains provided on the cylinder heads of the respective banks, for driving engine valves for the cylinder bores, respectively, to open and close; and valve operating characteristics changing mechanisms incorporated in the valve trains of at least one of the respective banks, and being adapted to change operating characteristics of the engine valves in response to oil pressure control implemented by an oil pressure control valve; wherein the oil pressure control valve is disposed in a space produced between end portions of the contiguous banks at either of ends thereof in an axial direction of the crankshaft as the banks are offset from each other and the oil pressure control valve is attached to at least one of the cylinder heads.
In the first aspect of the invention, it is preferred that the oil pressure control valve is disposed on a side face of at least one of the banks in a direction in which cylinders are arranged, and in a space produced between end portions of the contiguous banks at either of ends thereof in the axial direction of the crankshaft as the banks are offset from each other.
According to the construction of the first aspect of the invention, the space is produced between one end portion of the banks and the other contiguous banks along the axial direction of the crankshaft, because the plurality of banks dispose to be offset from each other in the axial direction of the crankshaft. Since the oil pressure control valve is disposed in the space, there is no risk of the oil pressure control valve to protrude from the engine in the axial direction of the crankshaft, whereby the miniaturization of the overall multi-cylinder engine can be attained.
According to a second aspect of the invention, there is provided a vehicle multi-cylinder engine as set forth in the first aspect of the invention, wherein the oil pressure control valve is disposed in the space which is produced at an end side of the engine and is adjoined to a transmission. According to the construction of the second aspect of the invention, since a space above the transmission is open and the oil pressure control valve is disposed so as to adjoin to the space, whereby the service of the oil pressure control valve for maintenance thereof can be facilitated.
According to a third aspect of the invention, there is provided a vehicle multi-cylinder engine as set forth in the first or second aspect of the invention, wherein the oil pressure control valve is attached to the cylinder head in a range of a width thereof. According to the construction of the third aspect of the invention, the overall multi-cylinder engine can be made more compact with the oil pressure control valve so as not to protrude sideways from the cylinder head.
According to a fourth aspect of the invention, there is provided a vehicle multi-cylinder engine as set forth in any of the first to third aspects of the invention, wherein the pair of banks are formed in a V-shape on a projection drawing onto a plane that is normal to axial direction of the crankshaft extending in a transverse direction of a vehicle, and the valve trains incorporating the valve operating characteristics changing mechanisms and the oil pressure control valve are, respectively, disposed on only the cylinder head of one bank of the banks situated on a rear side of the engine as viewed in a longitudinal direction of the vehicle.
According to the construction of the fourth aspect of the invention, when the adverse effect occurred to the oil pressure control valve by running wind while the vehicle is running, the adverse effect is suppressed to as low a level as possible by disposing the oil pressure control valve at the rear of the engine in the longitudinal direction of the vehicle. Namely, the cylinder head of the bank is disposed ahead of the oil pressure control valve to function as a wall for shielding the oil pressure control valve from the running wind. Then the reduction in temperature of hydraulic oil is suppressed, where the hydraulic oil controls the pressure, which is controlled by the oil pressure control valve. Therefore the response of the valve operating characteristics changing mechanisms is maintained high. In addition, an oil path between the valve operating characteristics changing mechanisms and the oil pressure control valve can be made shorter.